Cathal

A few weeks ago, I set up an ADS-B listener, started uploading to FlightRadar24 with the ID T-EINN18 , and I’ve watched my ranking go up and up..

As of this morning (August 20th I have the 43rd highest ranking of 130 in Ireland, 3rd highest Shannon uploader, and worldwide ranking of 6204 of 23,000, and going up by ~2000 positions a day at the moment.

I’m using a RaspberriPi 2b, an RTL-SDR dongle, and RTL-SDR 22dB LNA, and the antenna is a self-built colinear coaxial cable antenna with 8 116mm segments taped to the inside of an upstairs window. The software is dump1090 and the Flightradar24 uploader. I’m seeing ~850 aircraft a day, and an average daily max range of ~170 nautical miles (250km). Not bad for €50 or so of an outlay! I can see planes about 8000 feet above Dublin and 11,000 feet above Knock. The curvature of the earth combined with the lack of height of the antenna prevents me from seeing any lower.

The ADS-B signals are transmitted by every commercial aircraft and by most private aircraft, on a frequency of 1090 MHz. The information transmitted includes at least the ID of the plane and it’s current position and speed. When these signals are collected and processed, aggregator websites like Flightradar24 can show the current state of our aeronautical skies.

Improvements planned are the installation of an ADS-B specific filter/LNA from the RTL-SDR people that is en route. I did get one already but that failed within a few hours of installation so the warranty replacement was sought. That addition should mean that I have a bette chance of hearing planes through the house and increasing the range between my southeast and the west, as the window the antenna is in is facing to my northeast.

It is fairly interesting to see what is possible with some fairly basic items and a bit of DIY electronical knowledge!

The KiwiSDR is a completely self-contained device, that consists of a Beaglebone Green micro computer, with an attached ‘cape’ that provides 30mhz of HF bandwidth to ~8 tuners. This means that (in one configuration) there are four tuners each with a waterfall available for use. Because the device is self-contained and accessible across networks without the use of a PC to host the tuning, there’s great flexibility in the device that can play and display the radio signals.

I’ve mine set in a configuration where there’s only two tuners with waterfalls, but there are another four allocatable tuners as a result. I’ve also got a number of those tuners operating as a reporter for WSPR signals on 60m, 40, and 20m.

Currently the antenna feeding this SDR is a ~20m random longwire strung across the rear lawn in a North/South direction, feeding 50m of coax cable and ending up at a Nooelec 9:1 unun. There’s a reasonably low noise level on this antenna for some reason, though the signal level is also a tad low. I have plans for either an Active Antenna amplified loop antenna, or something like a Wellbrook loop or a Bonito amplified dipole

I’ve had a bit of time to try out a few different antenna ideas, and it’s been a very interesting learning curve so far.Self-build antenna fun: The first antenna attempt was a simple short randomwire of a few meters whiule sitting on the lawn with one of the laptops and the RTL-SDR dongle. I was able to get some SW stations from Saudi and Eastern Europe with that. Second antenna build attempt was that I set up about 20m of insulated copper wire across the lawn, and fed a coax cable to the receivers directly from the centre point. This gave reasonable results, but definitely left a lot to be desired. I tried better grounding of the coax sheath, and then I realised that I should try a proper centre fed dipole with one side earthed instead of both sides going to the signal feed. This improved things a little bit, but was still a little underwhelming, most likely due to the horizontal orientation and the 2m of distance from the ground. I rejigged the antenna in the third antenna attempt to become a proper ~20m long randomwire, end-fed to the signal feed in the coax, and earthing the coax cable at that point as well. This gave a good step up in sensitivity and signal strength. Then, after a long-awaited Ebay delivery of a 9:1 NooElec balun, things got quite interesting. I modified the balun to become a proper unun after breaking the centre tap to ground connection, and I installed the unun at the receiver. This is the current best state of the longwire, performance descriptions to follow. I had ordered a 4:1 voltage balun as an experiment. With 10m of cable each side, I had tried to have a 20m dipole with a proper correctly matching balun in DX operation. However, the experiemnt was not a success as I found that there was no LW or MW, and the signal/noise levels as seen by the receivers was quite low – lower than the pre-balun randomwire. This antenna has since been disassembled, but I’ll hold on to that balun for a possible future transmission antenna. After the purchase of ~200m of 0.5 square stranded cable, I decided to try a long loop around the perimeter of the property I’m currently living in. I ran ~80m of cable along the tops of the bushes and walls around the edge of the back lawn (maybe 2-3m average height), raising up to 6m height by using the soil pipe vent stack and a gutter downpipe as supports for the wire. I can’t yet put the wires muvh higher due to possible neighbour issues. Both ends of the wire loop were run into the radio room and attached to a 1:1 balun, and a length of coax then running to the receivers. The noise level is generally much higher than I had anticpated, and the signals are present at least. It’s a fairly good option at this stage if I had no other option. The balun in use has been shown to give some operation down to the LF area at least.Miniwhips. I started out with an AiExpress-sourced miniwhip, needing a 12v source, and 239 type connectors. I had a slew of 12v power supplies to hand, and found that the RFI generated by most of them was utterly abysmal and made attempting to use them for VLF through the lower end of SW almost impossible. . I did find the best of them, and it gave a clean enough power feed, and I did get to use that miniwhip to try to listen to things. Noise levels were still into the -60dBm with little in the way of useful SNR, and the signals were definitely not clear and listenable. I may yet disassemble this one and replace a few components to get a useful antenna. Then, I ordered a Chirio miniwhip with options of either 9v PP3 power or 5v bias-t power. This was a thinner antenna, and had ~6m of coax already installed with an SMA connector on the end. This antenna gave much better signal levels and a lower noise floor than the Chinese miniwhip, but still had a lot of crackling. Adding a better earth connection to the SMA connector on the cheapy Chinese upconvertor dropped the noisefloor by some 10dBm or so. I’ve currently got the antenna powered from the USB socket on the Pi3 that is hosting the FC0012 dongle and the rtl_tcp server that is serving this across my network. Antenna performances – as like-for-like as I can get them. The miniwhip has a noise floor currently of some -103dBm. With the RTL-SDR at auto gain and using 2048kHz bandwidth, Shannon Volmet at 5505 has a signal level of -80dBm., giving an SNR of 23dBm. The sound of the signal is not great, but definitely understandable. The horizontal loop with the 1:1 balun, with the Airspy, 2.5MHz bandwidth, linear gain at 15, zero visual gain, has the noise floor at -82dBm and the same Shannon Volmet signal at -71dBm, for an SNR of 11 dBm. The sound quality is poor, and not very understandable at all unfortunately. The randomwire with the 9:1 unun, with the RSP1a using 2048kHz bandwidth, RF gain at 9, IF at auto, and visual at zero, has a noise floor at about -134dBm and a Shannon Volmet signal of -103dBm for an SNR of 31 dBm. This signal sound is definitely the best of the three antennas currently in use. Receivers. I have a handful of RTL2832U dongles that I used when I was getting started in the SDR world. I’ve some FC0013 tuners, as well as an E4000 tuner. I bought two RTL-SDR 820t2 dongles with the antenna kits, and those were an absolutely fantastic introduction into the SDR world. The direct sampling mode is reasonable, though the lack of gain control is a bit of a pain. I’ve got one of the dongles set up with an upconverter on the Chirio miniwhip, and serving to my network. I later bought an SDRPlay RSP1a, and an Airspy/Spyverter combination. The RSP1a is pretty much the best bang for the buck SDR system that I’ve come across. VLF through 2Ghz without a break, no external upconversion required, usb-powered, and a lovely clean signal output. These are all very useful characteristics. The Airspy combo also has its place, it’s worth noting. Linux and RPi support is better, the hardware is physically smaller, and there are a few additional programs that are very useful such as the fast-sweep spectrum analyser and the ADSB client. Both of these receivers are currently plugged into the Dell Precision laptop, and being successfully served to my network via the SDR Console V3 server. When I’m working locally on the Dell Core I5 laptop, I prefer to use the Airspy combo with the 10Mhz bandwidth. If I’m listening to one particular signal. I’ll pick it out with SDR# and using the decimation feature, to get the best possible SNR for that signal. The 10Mhz is very useful for the general browsing of signals and seeing which one I want to home in on.Future plans: I’ve spent some time looking at the KiwiSDR as a useful addition to my radio listening system. The 30Mhz bandwith visibility, the perfectly networked interface, and the extra plugins currently available, added to the four separate receiver channels possible, are all very enticing for my use case. I also have my eyes on a better LW/MW antenna than I currentl have access to. I’m carefully eyeing up the likes of a Wellbrook ALA1530LN loop, or an Active-Antennas AAA-1 set as a quad loop, or even a Bonito Megadipole type of thing. I’m spending quite a bit of time looking round at the KiwiSDRs that are publicly available, to see how different setups can perform.

It’s been an interesting time recently, properly nerding out with the dabbling back into Software Defined Radio. Using a USB device, getting radio signals from around the world into the laptop, and doing interesting things from there. It’s pretty cool to be able, with the same device and hardware and antenna, to tune in the time signal on 60kHz, through getting shortwave radio stations from Botswana tuned in, to deciphering digital radio stations, to decoding the RTTY weather forecasts from the German weather service, to picking up faint FM radio stations from around the south of Ireland, to hearing Marine band transmissions, to seeing my car keyfob transmissions, to decoding and plotting airplane ADSB transmissions. All for under a hundred Euro for the hardware, and a few hours of learning.

It’s quite the rabbithole, is amateur radio stuff. Thinking about the HAM license and possible the VHF license as well, as those may come in useful for future outdoor adventures..

My lovely new 20″ scope appears to need glasses. Seems as though Skywatcher didn’t make the mirror as well as they should have, and there is somewhere around one to two waves of spherical aberration present on the mirror. This is ruining the fine contrast on planets and making the scope a little frustrating to use. Currently working with the vendor to get a replacement mirror.

There is also another issue with the scope, where the primary mirror support structure has enough movement present under the change in altitude, to ensure that the scope cannot maintain collimation. My investigations so far suggest that the movement is present only in the interface between the glass and the central aluminium column that mounts the mirror to the rest of the telescope superstructure, so that’s another reason to require the replacement of the mirror as I cannot easily perform a repair on that interface, and given it’s under warranty I’m not going to touch that one.

The third problem I was having was with the quality of the GoTo computerised drive system. It turns out that one of the core components that supports the telescope “tube” had been bent out of place during a shipping accident, and was interfering with the correct operation of hte altitude portion of the drive. One removal and re-addition later, that component is now in the correct position and I’m now getting the desired target object somewhere in the eyepiece field of view after a slew.

My impressions of the scope are still good, though tempered by the (hopefully) temporary optical and mechanical issues present. There are some things I really like such as the ease of setup and takedown and the subsequent ease of storage that results from that. The drive accuracy once pointed on target means I can do lucky imaging of deepsky objects with some interesting results. The requirement for a small stepladder is not an issue for me on a lawn, but may be an issue on an apartment terrace. Now that I have the best of eyepieces and a Paracorr, I have some pretty low-power views when it is dark, but the high power views definitely have suffered with the aberrations present.

There does exists the capability for this scope to be a fantastic performer, just not yet.

Just checking my phone today, I saw that there were three Facebook applications running on my phone. A Facebook app manager, a Facebook app installer, and “Facebook services”.

I’ve never explicitly logged into Facebook on this phone, and I’ve had the app completely disabled (couldn’t uninstall due to Three having baked this piece of crap into the ROM) since taking delivery of the device two years ago.

The Facebook service app had transferred some 8gb of data since Feb 20th. At least now those apps are denied running.

Pretty piss-poor of Facebook not to take the hint on my device and install on the background. Must try and see what apps carried that malware payload onto the device.

It looks like a good time to root the device and completely remove Facebook, as well as add all Facebook domains and IPs to the null device. I’ll do that when the warranty runs out.

Update: – It’s the update to Android Pie that carried these pieces of crap onto the phone. Now the updates to those apps are uninstalled and the apps are disabled. Not good from Three Ireland tbh to have these baked into the ROM.

My largest scope up to buying this one was a 12″ manual Dob, with some lovely views and memories from it. I had been hankering after an upgrade for some years though with the intent of getting a scope that would satisfy my aperture fever.. I wanted the largest aperture I could handle by myself, without needing to have it stored assembled. I’ve not got the room to keep a really large scope fully assembled so I needed to make sure I could assemble and disassemble whatever scope I got in a fairly short space of time given Irish weather, and without too much bother and faff, otherwise I’d just get tired of having to build each observing time.

I did my research on the scopes available, and this particular model started to filter up to the top of my shortlists. 20″ aperture, truss construction with no single piece heavier than about 30kg, generally reasonable to good optics based on other owner experiences, and a goto system utilising the well known Synscan handset, and the support of a large brand and a known-good dealer network.
I also knew that I would probably have some engineering to do myself with the scope, but I’m happy with that as I’m a bit of an old-school hardware hacker and tinkerer at heart. Fettling something does not phase me at all.

This particular scope arrived, and I spent a good while with the first assembly, figuring out what needed to go where, and what snafus were presenting, The manual is abysmal really, but the scope is not difficult to figure out to someone any way mechanically minded. I did need to add more counterweight but that was to be expected with a Paracorr and 100-degree eyepieces in the focuser. The focuser could do with an upgrade to a compression ring fitting at minimum but it does suffice for the purpose. The focuser movement is smooth and clean which is really useful! The truss construction with the ball and sockets construction method is well thought out, and means that collimation is fairly repeatable upon each assembly. The shroud is a lovely addition, though it did take me a little bit of time to realise that the velcro seam runs under the “tube” with the hole in the shroud near one edge actually goes over the focuser and finderscope. There are improvements that could be made to the shroud but it’s pretty good when tightened at the top and bottom over the truss attachment bolts. When tightened properly it does not come into the light cone and also provides a lot of stray light protection if one is observing in a not-dark location. The shroud also prevents body heat and exhaled breath from reaching through the light cone and affecting the views and optics. The goto system is reasonable, once aligned and synced on something in the neighbourhood the gotos are then fairly good. It’s a good idea to sync on a bright star near where the desired observing object lies, to get the best chance of getting that object in the eyepiece. There is an altitude stop that prevents the tube from getting to within 11 degrees or so of horizontal. I moved that stop to allow my scope to get to the horizon. There’s no apparent issue with that once I had the correct counterweights for my setup. I’m 5’10” tall, and I need a step or two once my target reaches above 37 degrees altitude, but I was expecting this for a scope of this size. I could not afford a scope with f/ratio of under 3 at this point. Two steps up a stepladder is all I need to get observing at the zenith, so it’s not too bad at all. I may invest in a good Catsperch chair at some point in the future. I’ll have to see how I go with a full night of being on a ladder. If there’s a breeze blowing and the shroud is on the scope, then there will be a bit of movement seen at the eyepiece. In general though the views are steady, and there’s no loss of target when swapping eyepieces out which is a real boon for me after using the 12″ where I’d have to re-find the target again.

As for the optical quality, I’ve not seen any issue yet that I’m worried about. My seeing is generally in the 2-4 arcsec range on average nights, under an Atlantic jetstream. I’ve had a few evenings out under mediocre skies so far, but I’ve been able to get E and F in the Trapezium pretty much with ease for most of time. Stars are scintillating balls of mush, but a ball of mush that is seeing-caused. No astigmatism showing up so far, no real roughness apparent based on my testing at this stage. When the mirror is cooling down it does show an undercorrection but this appears to lessen as thermal equilibrium is reached. I haven’t had a long enough session yet with the scope to be able to determine the finer optical quality, but that will be done in time. So far, I’m happy enough with the performance – it’s certainly the case that I’m being atmosphere-limited, and that’s a nice place to be.

One thing that is really of interest with this scope, is that it appears to be exceptionally suitable for Electronically Assisted Astronomy, and for Lucky Imaging of DSOs. The f/ratio of under 4 and the aperture of a half-metre means that deep exposures can be obtained in a very short space of time.. I got to about mag 19 with about 4 min worth of 1.7 second subs with an ASI294MC-Pro, and seeing that result had my jaw hit the floor. The tracking is probably not good enough for multiple tens of seconds of sub lengths, but a low noise camera and a lot of disk space will work wonders..

The known issue of mirror flop causing collimation skew when changing altitude is fairly easily resolved, and I have also added a Kendricks secondary dew heater as I’ve had the secondary mirror dew up when not using the shroud. I may yet add a boundary layer set of fans and fans blowing at the rear of the primary to aid in thermal equilibrium

If you are in the market for a transportable half-metre telescope that one reasonably fit person can assemble and disassemble with relative ease, that provides lovely eyepiece images, and that does not cost the earth, then the Skywatcher Stargate 500p is a scope that should be high on your list.

It’s a Skywatcher Stargate 500p Dobsonian truss-type telescope. The primary mirror is a full half-metre wide, it has a 2 metre focal length. It’s an absolute light bucket. It comes with a computerised goto drive, and it takes me less than about 10 min to set it up and have it running.

It came in 4 large boxes, with a shipping weight of about 95 kg.

I updated my eyepiece collection to suit the f/3.94 focal ration, with a Paracorr, a few Ethos 100-degree eyepieces, and a widest-field Explore Scientific 25mm 100 degree eyepiece. I now understand exactly why people got for the green eyepieces when they can..

The views through this scope are, not surprisingly for a 20″ scope, absolutely spectacular. Theoretically from a dark sky this scope should get visually down to mag 16.2 or so. Trying my hand at some Electronically Assisted Astronomy with the ASI224MC I got a nice view of the core of M42, about 2 min of stacking of 1/8th second (!) exposures and managing to capture some of the proplyds (nascent star solar systems):

Using the larger 4/3rds OSC CMOS camera that I also got recently (an ASI294MC-Pro) I stacked 2 second subs for ~4 min to get this M1 Crab nebula with lots of detail and down to mag 18 stars:

After a while the conditions overhead deteriorated poorly to the point where I could not make out the shape of Leo and the Plough asterism was becoming invisible. I persisted with taking subs of M51 to get this pic:

Overall – I’m *really* impressed with how this scope is performing for me. It’s a little bit of a bother to disassemble and reassemble and the heavy bits are rather awkward to try and get through a door – but they fit through a door. I’ve also found that I can strap the scope to a handcart and maneuver around the garden with ease, which bodes well for outreach with Astrosoc.

I have not yet had an opportunity to check a Moon or either of the large planets in the morning sky yet, really looking forwards to that..

I got my hands on a Xeon E5-1680V2 processor last week. This is about the best CPU that I could get for my motherboard, and it’s an overclocking monster. Comfortable at 4.7Ghz at <80 degrees, currently at 4.6 and staying under 75 after extended benchmarks.

Adding to this the fact that I finally jumped 4 generation of graphics cards by updating to a Zotac 2080 Amp MAXX card, gaming and GPU computations are now impressive. All games at max details at 1980×1200 (none of that tiny HD resolution) now are pretty much stable at 60 FPS, and oh *so* pretty.

After having to update the PSU to a decent Corsair HX850i it now runs without clocking down or bluescreening in games, and makes me quite a happy camper. The PC name as “Behemoth” is still very much relevant. Pretty much the only update left for the PC is to go to 4x4Tb drives for the RAID array. No real cost benefit to going any newer or bigger or better with any of the components.

Not too bad for a system originally built some eight years ago, and still on the same motherboard, memory, and spinny disks. Updates to CPU/GPU/system SSD did happen over time.